Thermostat



A. A. STRAND THERMOSTAT May 24, 1938.

3 Sheets-Sheet 1 Original Filed Aug. 8, 1934 mvEN roR Higg ns, fl Sim/1a! BY i v; 16 7 ATTORNEYS A. A. STRAND May 24, 1938.

THERMOSTAT 3 Sheets-Sheet 2 Original Filed Aug. 8, 1934 INVENTOR flqgus/fl Sirarml AlToRfjEY A. A. STRAND THERMOSTAT' May 24, 1938.

Original Filed Aug. 8, 1934 3 Sheets-Sheet 3 INVENTOR gzgg'usffl J/rand @A 151,

ATTORNEYS Patented May 24, 1938 UNITED STATES PATENT OFFICE Application August 8, 1934, Serial No. 738,920 Renewed October 20, 1937 2 Claims.

The invention relates to controlling temperature, and more particularly to thermostats.

The objects of the invention include the provision. of a relatively inexpensive, dependable,

highly efficient and sensitive device of the type above indicated.

Various further and more specific objects, features and advantages will clearly appear from the detailed description given below, taken in connection with the accompanying drawings which form a part of this specification and illustrate, merely by way of example, embodiments of the invention.

In the drawings:

Fig. 1 represents a vertical section through the thermostat;

Fig. 2 is a section on. the line 22 of Fig. 1 illustrating the solenoid and snap switch;

Fig. 3 is a section on the line 3--3 of Fig. 1;

Fig. 4 is a side elevation of the thermostat;

Fig. 5 is a detail illustrating the construction of the combined binding post, brush and switch assembly;

Fig. 6 is a section on the line 66 of Fig. 3;

Fig. 7 is a section on the line of Fig. 1;

Fig. 8 is a section on the line 88 of Fig. 3 illustrating the roller and spiral contacts;

Fig. 9 is a diagrammatic view illustrating the connections; and

Fig. 10 is a section on the line Ill-l0 of Fig. 2.

In the following description and in the claims, various details will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit.

Like reference characters denote like parts in' the several figures of the drawings.

In the drawings accompanying and forming part of this specification, certain specific disclosure of the invention is made for purposes of explanation, but it will be understood that the details may be modified in various respects without departure from the broad aspect of the invention.

, Referring now to the drawings, the thermostat 0 comprises, in general, a base l0 which may be fitted directly to an outlet box (not shown) and a detachable cover |8 enclosing the mechanism. The thermostat mechanism comprises a bellows L0 assembly 32 which drives a contact roller 58 which rolls on spiral contacts 43 and 44 mounted on the adjustable insulating drum 34. The contact between roller 58 and contacts 43 and 44 controls a solenoid ll, 18 which operates a snap 55 switch 81 and bridging contacts 88, 89. The

main snap switch 81 controls the load or other mechanism it is desired to govern.

The insulating base l0 may be mounted at any desired point, as for example, on an outlet box as disclosed and explained in detail in copending application Serial No. 738,919, filed August 8, 1934. The detachable cover I8 is secured to the base in the manner disclosed in the copending application just mentioned. Briefly, the detachable cover l8 has ventilating openings .24 in its side walls, an 10 opening in its front wall for the adjusting knob 23 by which the temperature is set and a sight hole 2| through which temperature indications, printed on wheel 22, may be viewed.

The framework of the thermostat comprises a 15 U-frame 28 secured to the insulating base In and having a guide hub 30 for the bellows rod 33. A U-brace 29 bridges the U-frame 28. A top bracket 3| is provided for anchoring the fixed end of the bellows assembly 32.

The bellows assembly 32 is described in detail in copending application Serial No. 569,916, filed October 20, 1931. Briefly, it comprises a stack of gas filled bellows units suitably secured together to the lower end of which is fixed the rod 33. The rod 33 drives the contact arm 51 supporting contact roller 58 in a manner explained hereinafter more in detail.

The spiral contacts 43 and 44 are mounted on an insulating drum 34 fast on bushing 35 jour- 30 nalled in U-frame 2S and mounted on shaft 38. The indicating plate 22 is rigidly mounted on a reduced shoulder or bushing 35 and is held in position by screw 31. Shaft 36 is held lengthwise by screw 31 and a small plate 38 on U-brace 29. 35

The spacing washer 39 is positioned between indicating plate. 22 and frame 28 and a spring washer 40 holds the insulating drum 34 and assembly snugly against the frame 28.

The adjusting knob 23 is mounted on a stud 40 shaft 62 and is provided with gear teeth meshing with gear teeth on the indicating plate 22. The insulating drum 34 is provided with collector rings 4| and 42 contacting with brushes 60, 5| (Fig. 6)

The spiral contacts 43, 44 are mounted on the insulating drum 3 and are disposed as illustrated especially in Figs. 3 and 9. The insulating piece 45 separates the spiral contacts 43 and 44 providing a continuous mechanical path for the roller 58 on the spiral contacts 43 and 44. Electrical connections are provided between contacts 43 and 44 and rings 4| and 43, as illustrated. Protective coatings of thin sheet silver 46 are placed on the adjacent ends of spiral contacts 43, 44 to take the arcing, as illustrated especially in Figs. 4 and 8.

For driving the contact roller 58 from bellows rod 33 an articulated support is provided. This support comprises a T-shaped member 1?, U- shaped in cross section having a forked end which is pivoted to rod 33 by pivot The other end of member All receives an angular spring 56 wound about a pivot 5i passing through the member ll. The end of spring 5i) has a hook and a second hook 453 is provided on the upper end of member 41 between which is suspended a cable 52 which is wound several times about shaft 53, the cable being kept under tension by spring 59.

The drum. or shaft is mounted on shaft 36 (Fig. 1). The drum contacts at its ends only with shaft 36 to reduce friction. Mounted on drum 53 is an insulating ring Ed on which is mounted a collector ring 55, maintaining contact with brush 59.

Secured to collector ring 55 is a spring ring 56 supporting arm 5'5 on which is journalled roller 58 for both rotational and axial movement on the arm 57. Spring ring 56 is secured to collector ring 55 at a point opposite the arm 5i only so that the spring ring 56 normally tends to take a position away from the ring 55 to yieldably hold the roller 58 on its spiral contacts t3 and M.

The construction of the articulated support assembly, the insulating drum assembly supporting the collector rings, spiral contacts and the contact roller assembly are disclosed more in detail in the above mentioned copending application.

Instead of using the engagement between roller 58 and spiral contacts is and M to control the main controlling current which governs the heating system, in certain instances, it is more desirable to utilize a solenoid operating a snap switch for controlling the main control current. This is especially desirable when operating the thermostat on 110 volts.

Mounted between the brace 29 and insulating base it is a solenoid it made up or" electromagnets El! and 18. These electromagnets are supported by a curved holder 75 secured both to the insulating base and to the frame 28, 29. The holder 15 has end tongues (Fig. 3) for fixing the axial position of the electromagnets, the brace 29 maintaining the electromagnets in spaced position.

Each electromagnet 11 or "iii has the same con" struction so only one will be described in detail. Electromagnet ii is made up of a center sleeve 89, an outer sleeve 353 and end washers 8i and 82, all made of suitable strong insulating material and secured together to protect the winding enclosed.

Disposed within the electromagnets 5?, i3 is a plunger made up of cores 83 and 84 secured together and carrying an insulating arm 85 which slides along on the insulating base it to hold the core assembly in proper angular position. The insulating arm 35 carries a pair of holder strips 86 (Fig. 2) which engage the snap switch 8? in a manner hereinafter described more in detail. The insulating arm 85 also carries a pair of bridge contacts 88 and 89 having enlarged contact terminals and cooperating with a pair of combined brush, switch and binding post assemblies, as illustrated especially in Fig. 5.

The snap switch 37 (Figs. 1, 2 and 10) comprises a frame 96 made of a metal stamping secured to the insulating base iii and having extensions providing upper recessed outer seats 9! and lower recessed inner seats 92 for the pointed legs of U-shaped switch members 93 and 94. Switch member 54 carries contact 95 cooperating with the stationary contact ill mounted on the insulating base. Switch member 93 carries an eye between which and a similar eye on contact 95 is connected a spiral spring 96. This spring 96 operates to hold the legs in their seats and the snap switch. in assembled position and also operates to give a snap toggle action which will be understood by those skilled in the art. If desired, in order to increase the carrying capacity of the switch, flexible pig tails may be connected between U-shape member 94 and frame SEI.

Referring now especially to Fig. 5, the assembly comprises a U-contact 98 mounted on the insulating base in electrical contact with the brush E59. An insulating bushing 99 is provided on which is mounted a U-contact its. A binding screw lfii holds these members in assembled position and passes through the insulating base where a suitable nut holds the structure fast. The other combined brush, auxiliary switch and binding screw assembly is of the same construction except that it incorporates brush (ii instead of 60.

Connections and Operation Referring to Fig. 9, the electrical hook up of the parts is shown with the same reference characters, as used in the mechanical figures used as far as possible. As illustrated, it will be assumed that the thermostat is not calling for heat and that the room is above the desired temperature. As the temperature of the room drops the bellows 32 will contract, causing the arm 51 to move downwardly in Fig. 9, the roller 58 rolling across, say, from spiral contact 43 to spiral contact M. This will complete the circuit through collector ring :32, brush 6!, auxiliary contacts 89, electromagnet ll, causing the latter to operate immediately, breaking its own circuit and closing contacts 88 putting the circuit through spiral contact 43 in readiness for when the contact arm 57 moves the other way. The operation of the solenoid also closes snap switch 8?, closing the circuit to the load for the controlling device for turning on the heating system.

As the temperature of the room increases, the bellows 32 will expand moving the roller 58 back across to make contact with spiral contact 43. Contact between roller 58 and contact 43 will then close the circuit through the other electromagnet 78 breaking the main contacts 95, 91 and turning off the heat. It will be noted that no current is ever broken at the roller 58, but all of the current is broken at the contacts 88 or it which has a snap action. Consequently, the only arcing that can occur at the roller 58 is a slight arc due to make. This is amply taken care of by the very thin silver protective layer 46.

To adjust the thermostat to a difierent operating temperature, it is only necessary to move the knob 23 and observe through sight hole 2| the temperature markings on gear 22. This rotates the entire insulating drum 3d and assembly. Thus a wide range of operating conditions is provided for. The thermostat may be used to keep a room heated, say, at 70 and then if it is desired to use the same thermostat for keeping the temperature at, say, 30, it is only necessary to change the adjustment stated above. The long length of spiral of the contacts 3, 44 allows a great range of movement for the roller 58 which may be necessary if, for any reason, the

heating or cooling mechanism should fail or if the adjustment is manually changed.

Another advantage of the present construction is that it may be used directly in a conventional 110 volt household system and that it is not necessary to provide dry cells or other local sources of current of reduced voltage. It may be operated either on direct current or alternating current.

It will be noted that the current passing through electromagnet 11 or 1B is but for an instant duration and consequently no error can be introduced into the thermostat due to local heating. Furthermore, due to the fact that the main contacts 95, 91 are of considerable size, the switch may be used to govern a control current of considerable amperage.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art Without departing from the spirit of the invention.

What is claimed is:

1. In a thermostat, an insulating base, a pair of spaced aligned solenoids mounted on said base, a core within said solenoids, an operating arm carried by said core between said solenoids, and slidable on said base, a. snap switch on said base operated by said arm, said arm also carrying on opposite sides thereof a pair of bridging contacts, a pair of sets of contacts bridged by said bridging contacts, each said set comprising an upper contact and a lower contact mechanically supported by the same binding post on said base, a brush supported by said binding post, and collector rings contacting said brushes.

2. In a thermostat, an insulating base, a pair of spaced solenoids mounted on said base, a core within said solenoids, an operating arm carried by said core between said solenoids, a snap switch on said base operated by said arm, said arm also carrying a pair of bridging contacts, a pair of sets of contacts bridged by said bridging contacts, each said set comprising an upper contact and a lower contact mechanically supported by the same binding post on said base, a brush also supported by said binding post, and collector rings contacting said brushes.

AUGUST A. STRAND. 

